Stormy Weather

An Internet guide to extreme weather

One thing I miss, living in southern California, is weather. Sure, it rains a little in the winter, but I have yet to see a decent, violent thunderstorm in Los Angeles—nothing like the spectacular lightning shows that would roll across New York City, where I once lived, or my native Virginia. On the Internet, however, there is always a good storm brewing at the site of the Convective Modeling Group at the University of Illinois at Urbana-Champaign. A leader in visualizing the complex airflow that creates huge thunderheads and tornadoes, this group’s supercomputer simulations are aimed at solving some of the mysteries of violent storms and have been used to illustrate IMAX films.

Click on “Image Gallery” in the menu on the left of their home page. Here, you will find a showcase of their efforts. Click on “Education” instead, and you will be directed to the university’s Weather World 2010 Project. From this site’s left-hand menu, select “Online Guides” and then “Meteorology” to find pages covering various types of severe storms. Under the heading “Severe Storms” and then “Dangers of Thunderstorms,” I discovered that the softball-sized hailstones I once saw falling in Dallas, Texas, were perhaps not the biggest. According to the site: “Hail rarely kills people, but these were hollow words in China in May 1986, when 100 people were killed, 9,000 injured, and 35,000 homes destroyed by an intense hailstorm.” Another site that has computer simulations to help us see into the heart of violent storms is at National Center for Atmospheric Research. Click on “Select a Category” and choose “Severe Weather” to view the storm clips.

A number of Internet sites explain the basic forces that drive large storms. The Canadian Geographic has a page on the Anatomy of a Thunderstorm, with a video clip that describes how rain and hail form in the rising columns of moist air of storm. At a site in the United Kingdom (School Portal) there is an animated cartoon to help you visualize the role of advancing cold fronts in generating thunderstorms. The animation, credited to Prentice Hall, also shows the geometry of advancing warm fronts, if you click on the button in the lower right—see how the two systems create different kinds of clouds. The Educypedia, the Educational Enyclopedia has more links to various atmospheric science animations and java applets. For more detailed explanations of a host of meteorological phenomena, try Understanding the Atmosphere, a collection of educational applets by Tom Whittaker and Steve Ackerman at the University of Wisconsin at Madison. Scroll down to Chapter 11 for material on thunderstorms and tornadoes. For instance, click on “Grow a Thunderstorm” and you can learn how to manipulate moisture and temperature to create the perfect storm.

At the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory I found a page of frequently asked questions that answered mine: Why doesn’t southern California experience more thunderstorms? The answer: “There is less convection on the west coast in part because of the cool water temperatures off shore in the Pacific Ocean. That impacts the temperature of air that moves inland, making it generally more stable and less convective (convection = thunderstorms). To get thunder you need strong updrafts (convection), which means rapidly falling temperatures with height (vertically) in the atmosphere.” Elsewhere at the site is a page on Severe Thunderstorm Climatology. Here the lab has animated maps displaying the year-to-year changes in tornado, severe wind, and hail patterns.

In the news archive at NASA’s Goddard Space Flight Center news room, you can learn how global thunderstorm activity is mapped. Apparently, Argentina, just east of the Andes, has the most intense storms, while Central Africa is, by far, the place to go for lightning (Florida, if you’re in the United States).